This invention relates to a balloon catheter having a novel balloon.
A balloon catheter having an inflatable balloon secured at its distal end has been applied for various cavities in a living body including a blood vessel. Utility of the balloon catheter is increasing in various medical fields.
Of the balloon catheters mentioned above, a blood vessel-dilating catheter is employed in percutaneous transluminal coronary angioplasty (PTCA) to dilate a stenosis or a narrowing in a blood vessel such as coronary artery or percutaneous transluminal angioplasty (PTA) to dilate a stenosis or a narrowing in a peripheral blood vessel. In PTCA, femoral artery is secured, for example, by Serdinger method; the distal end of a guiding catheter is introduced into the thus secured femoral artery and advanced through the lumen of the artery until it reaches the entry of the target coronary artery; a blood vessel-dilating catheter is introduced into the lumen of the guiding catheter to locate the balloon at the narrowing in the blood vessel; and a blood vessel-dilating fluid is introduced into the lumen of the blood vessel-dilating catheter to inflate the balloon to thereby dilate the narrowing in the blood vessel.
Such a blood vessel-dilating catheter is required to have a trackability so that the blood vessel-dilating catheter can smoothly advance through the lumen of the guiding catheter along the tortuous blood vessel to reach the lesion site. The balloon is required to have a sufficient dimensional stability as well as excellent strength and flexibility so as to avoid excess dilation of the narrowing of the blood vessel.
Typical balloons for balloon catheters are disclosed in U.S. Pat. No. 4,093,484; 4,154,244; 4,254,774; 4,906,244; and 5,108,415; and PCT Application No. JP88/00202.
The balloons described in these patents and patent application comprise for example mixture of an ethylene-butylene-styrene block copolymer and a low molecular weight polystyrene having polypropylene optionally added thereto; a composition similar to the one just mentioned wherein butadiene or isoprene is used instead of the ethylene and the butylene; polyvinyl chloride; polyurethane; a polyester copolymer; a thermoplastic rubber; a silicone-polycarbonate copolymer; an ethylene-vinyl acetate copolymer; biaxially oriented Nylon 12; biaxially oriented polyethylene terephthalate; polyethylene; and a crosslinked ethylene-vinyl acetate copolymer.
The material particularly used for the balloons of the blood vessel-dilating catheters include polyvinyl chloride (hereinafter abbreviated as PVC), polyethylene (hereinafter abbreviated as PE), biaxially oriented Nylon 12 (hereinafter abbreviated as N12), and biaxially oriented polyethylene terephthalate (hereinafter abbreviated as PET).
Among these, aliphatic high polymers such as PE, PVC and N12 are highly flexible, realizing a sufficient trackability. These materials, however, are insufficient in their strength to detract from dimensional stability.
PET, on the other hand, has excellent strength and dimensional stability. PET, however, has an excessively high modulus of elasticity due to crystallization caused by the biaxial orientation, and therefore, is inferior in impact strength, tear resistance and flexibility, leading to poor trackability of the catheter.
Furthermore, PET is poor in coating adaptability, adhesibility, and heat sealability and results in balloon catheters comprising inadequate operativity and workability. In addition, PET inherently lacks antithrombotic properties, and it would be quite difficult to subject the PET to various treatments to impart biocompatibility, in particular, blood compatibility.
Since medical instruments are used directly in human bodies, they need to be sterilized and pasteurized for safety. Since prior art catheter balloons made of PE, PVC, N12 and PET are inferior in heat resistance and radiation resistance, they cannot be subjected to autoclave sterilization and .gamma.-ray sterilization. Therefore, they have been subjected to sterilization in an atmosphere of an ethylene oxide gas (hereinafter abbreviated as EOG). However, after sterilization EOG remains on the product. Moreover, since EOG causes hemolysis, it is necessary to remove the EOG, which removal process takes about a week. This results in safety and productivity problems.
The present invention has been achieved in view of the above-described situation. An object of the present invention is to provide a balloon for a balloon catheter wherein the softness and the flexibility are improved without compromising the dimensional stability . Another object of the present invention is to provide a balloon for a blood vessel-dilating catheter wherein the modulus of elasticity is reduced to prevent an injury of the blood vessel inner surface.
According to the present invention, there is provided a balloon for a balloon catheter fabricated by molding polyarylenesulfide (hereinafter abbreviated as PAS) or a polymer alloy thereof comprising PAS as one of its components.
Also, according to the present invention, there is provided a balloon for a balloon catheter fabricated by multi-layered extrusion molding of PAS and olefin.
The PAS may preferably be at least one selected from the group consisting of polyphenylenesulfide (hereinafter abbreviated as PPS), polythioether ketone, polythioether thioether ketone, polythioether ketone ketone, polyether thioether, polythioether sulfone, polybiphenylene sulfide and polynaphthalene sulfide.
The PAS may preferably be a high molecular weight PPS.
The balloon preferably has a calculated modulus of elasticity of from 70 to 200 kg/mm.sup.2.
The balloon may preferably has a burst pressure of at least 10 kg/cm.sup.2.
The balloon film being fabricated by PAS or a polymer alloy thereof comprising PAS as one of its components may preferably be oriented biaxially.